An inverter circuit is used to convert the electric power (direct current) stored in an electric power storing device into alternate current so as to supply alternate current power to loads. The utility model patent with a publication number of CN203951381U discloses an on-board inverter system, as shown in FIG. 1, which comprises a direct current power source 1, a filter circuit 2, a Boost circuit 3, a DC-DC Boost circuit 4, a DC-AC inverter circuit 5, an alternate current filter circuit 6, a voltage measuring circuit 11 and a controller 10 for controlling the Boost circuit 3, the DC-DC Boost circuit 4 and the DC-AC inverter circuit 5.
Because an inductive load (such as a motor) has very large starting current (normally 4-7 times of the rated current), it also has very large starting power which is much larger than the rated power of the inverter circuit and may cause damage to circuit components.
In prior arts, in order to solve the above-mentioned problem, an industrial frequency transformer is arranged at the input side of the DC-AC inverter circuit 5, so as to enable the inverter circuit to be loaded with an inductive load by utilizing the transformer's characteristic of outputting a reduced voltage when the load current increases. However, the industrial frequency transformer is bulky and has a large weight, which brings about inconvenience of being carried around and moved.